Gas operated blasting cartridge



March 9, 1965 s. THOUZEAU GAS OPERATED BLASTING CARTRIDGE INVENTOR GEORGES THOUZEAU Filed Jan. 19, 1961 ATTORNEY United States Patent 3,172,361 GAS OPERATED BLASTING CARTRIDGE Georges Thouzeau, Verneuil-en-Halatte, Oise, France, assignor to Charbonnages de France, Paris, France, a public institution of France Filed Jan. 19, 1961, Ser. No. 83,705 Claims priority, application France, Jan. 30, 1960, 817,165 2 Claims. (Cl. 10225) The present invention relates to improvements in or relating to air blasting devices of the type wherein a gas compressed to a very high pressure enclosed in a container is abruptly expanded by the rupture of a plate or actuation of a piston under the effect of the gas pressure, and injected through vents into the rock mass to be blasted or shattered.

More specifically, the invention provides improvements in devices for introducing compressed gas into the said container.

The invention applies to the method of introducing highpressure gas, which is generally compressed air, into the container which is closed by the device adapted to yield and be displaced under the action of the pressure.

It is known that, in the aforesaid devices, the compressed gas in introduced into the container through a tube extending to the neighbourhood of the yieldable and/or movabe device, so as to provide a cooling action.

Numerous tests carried out by the applicant have shown that this cooling device was not sufficient to prevent certain occurrences due to the entrainment of lubricating oil from the compressor into the container of the blasting device. In spite of very comprehensive rules for the use of the device, sufficient precautions are not always taken to prevent oil from being so entrained. Repeated tests have shown that the entrainment of oil could entail risk of explosion in the container of the blasting device at the time of its being filled.

It has been shown by other tests carried out by the applicant that, by judiciously piercing the compressed-gas feeding tube, the danger of a sudden ignition of oil in the container of the blasting device when being filled could be reduced and even completely eliminated.

The disclosure of some of the aforesaid devices points out that the compressed-air supply tube can be provided with apertures for discharging a portion of the air at other points where it is desired to produce a cooling effect. But tests by the applicant have shown that the number, the position and the cross-sectional area of the apertures are far from being unimportant if any risk of oil ignition is to be obviated.

It is possible that elimination of the danger of oil ignition is connected to a suitable distribution of the cooling effect due to the mixing of the fluids, but nothing can be held to be certain in this respect. Whatever be the correct explanation and without being able to prove any particular one, it has been shown by repeated tests that suppression of the danger of oil ignition can only be achieved by as regular as possible a distribution and as regular as possible a mixing of the fluid introduced into the container, with a minimum of four apertures. Under the most severe conditions, a complete effect is achieved with a minimum of eight judiciously placed apertures. In practice, it seems that the best result would be obtained by arranging the orifices and selecting their cross-sections such as to effect an equalisation of pressure throughout said container at all times while filling the container. The physical reality is perhaps different, but nevertheless a new effect can thus be obtained.

3,172,361 Patented Mar. 9, 1965 The invention is characterised in that, in an air-blasting device wherein the blast is effected by a sudden expansion due to the provision of means yieldable and/ or movable under pressure, the tube for the introduction of the compressed gas having a length equal to or greater than twothirds of the length of the container, has a minimum of four lateral apertures.

In accordance with another feature of the invention, the cross-section and the position of these apertures are so corelated that the mass of fluid introduced per unit volume of the container is substantially constant at any given moment over the entire length of the container.

In accordance with a preferred embodiment, the length of the compressed gas supply tube is at least equal to fourfifths of the length of the container.

In accordance with a further feature, the lateral apertures are of increasing cross-sectional area commencing with those nearest to the tube inlet until those nearest to the extremity of the tube in the case of a cylindrical container.

In accordance with a still further feature, the spacing of the lateral apertures decreases from the inlet to the extremity of the tube.

According to another feature, the orifices are arranged in one or more helices.

In accordance with a preferred embodiment, the compressed gas supply tube comprises a minimum of eight lateral openings.

Other features and advantages of the invention will become clear on reading the following description with reference to the accompanying drawing, in which:

FIGURE 1 shows diagrammatically the tube test arrangement;

FIGURE 2 shows diagrammatically a firing container provided with a gas input tube having four orifices formed therein; and

FIGURES 3A-3B and 4 show, diagrammatically, modified embodiments of compressed gas input tubes in accordance with the invention.

Tests have been carried out under firing conditions in which the danger of oil explosion is maximum.

An oil reservoir 1 having a capacity of a few hundred cubic centimeters immediately follows the firing valve 2 (compressed air inlet valve). A pipe 3 of as small a length as possible (10 m.) connects the unit comprised by the firing valve 2 and the oil reservoir 1 with the con tainer 4 provided with a plate 7. The firing containers under test are cylindrical and have an internal diameter of 63.5 mm.

The compressed air supply tubes 5 are made of copper, have an internal diameter of 4.5 mm. and an external diameter of 9.5 mm. They penetrate into the container 4 provided with a coupling 6.

The tube diagrammtaically illustrated in FIGURE 2 is a firing container 4 provided or not with a compressed gas supply tube 5 penetrating into the tube 4 from a coupling 6. As in the case of FIGURE 1, a plate (not shown) closes the firing container; this plate yields under a given pressure and releases the gas into the rock mass to be blasted or shattered through vents 8 (FIGURE 1). This tube has two holes 9, which are preferably diametrically opposed, have a diameter of 1.3 mm., are located in the coupling, and, if desired, have two further holes 9 (which are also preferably diametrically opposed) located at a distance d from this coupling. Dilferent types of tubes have been tested having the following characteristics (the references used in the following table as well as in those further on are as given in general in FIG- URE l).

3 A. Table l The combustible oils used for the tests were a cornmercial lubricating oil and a commercial gas oil. inder L th f g gi g Du etlr these test conditions, the commercial gas 011 IS distinctly O B o l m l/ 'Type' @25 1? Length of tl l con'fadditional oithe more inflammable than the commercial lubricating 011. Oftube container, Pressed orifices mammal For a better understanding of the results, it is to be (figure firing rum. air supply from the orifices, 5 n

2) tube, mm. tube, mm. coupling, min. further pointed out that the IlSk or air-oil explosion inside the firing container increases when the mean presa b c d 6 sure of the compressed air which causes the rupture of the plate plugging the container increases. This effect has A 1 388 $8 10 been demonstrated by repeated tests. @1111: 21 650 21 460 Table 111 gives the results obtained for firing tubes of g $88 2% two lengths (170 cm. and 265 cm.) with or without pery forated inlet tubes of the types defined in Tables I and II.

Table III Length of Mean rup- Frequency Test Type of compressed Amount of ture pressure of explosion No. Type of combustible oil tube air supply oil, cc. of plate 7, in the con tube, mm. kgJsq. cm. taincr (luring firing Commercial Lubricating 01L. 1, 266 50 105 4/5 do 50 405 3/5 2, 240 100 600 3/7 1, 290 100 600 0/10 1, 260 50 405 0/10 1, 260 100 4.05 o ro 1, 260 100 780 0/10 1, 260 100 390 0/10 1, 260 100 780 0/10 2, 240 100 300 /5 2, 240 100 600 0/10 1, 260 100 600 1/1 1, 400 100 600 1/1 1, e 100 can 0/10 1, 750 100 600 0 10 2, 240 100 650 0/10 On the other hand, firing containers in accordance with the invention whose compressed air input tubes are provided with orifices 9, the first two of which are located adjacent the inlet coupling or in this coupling (FIGURES 3A and 3B) and the others as shown in i Comparison between tests Nos. 1, 2, 3 and 10 on the the, one hand, and tests Nos. 4, 5, 6, 7, 8, 9, 11 and 16 on the other hand, shows that the danger of oil-air explosion is greatiy reduced by the use of an inlet tube in accordance with the invention.

Table H, have also been tested. Moreover, tests Nos. 12, 13, 14 and 15 show that Table 11 Overall Length of Distances Successive length Length of the combetween 2 diameters of Type of of the container, pressed Total orifices orifices from tube firing mm. air supply number (other than the first two (figures tube, mm. tube, mm. of the first to the ex- 311 and 3B) orifices two), mm. tremrty, mm.

a h c e G 2, 650 2, 460 8 fi c 1. 3-1. 5-2 2. 3-3. 5 4

1 See Table III.

In the tubes F and G, the orifices are thus arranged in the following manner:

The first two orifices are of identical diameter, are disposed either in the coupling 6 or a few centimeters from this coupling and are diametrically opposed in the tube. Those following are at distances and have diameters as shown in Table II. They are arranged helically so that two successive orifices are located on generatrices of the tube at 90 to each other.

In accordance with the alternative embodiment shown in FIGURE 4, the orifice 9 have the same diameter (1.5 mm.), the distance between two successive orifices decreasing from the first two which are adjacent the coupling 6 up to the extremity of the tube. Thus, advantageously:

there is a minimum length for the tube having apertures in order to preclude oil-air explosions in the firing container.

Experience has shown that, in using this type of equip ment, it may happen that the compressed gas supply tube becomes twisted or spiralled. Tests carried out by the applicant have shown that, beyond a certain length of the apentured tube, spiralling due to compressed air has no eifect on safety. This minimum length is fourfifths of the length of the container.

The above disclosure relates to tests carried out with containers of the type provided with a plate. However,

the results may be applied to all kinds of firing containers operated by the expansion of a compressed gas.

Although the present invention has been diescribed in conjunction with preferred embodiments, it is to be understood that modifications and variations may be resorted to without departing from the spirit and scope of the in- 5 vention, as those skilled in the art will readily understand.

Such modifications and variations are considered to be Within the purview and scope of the invention and appended claims.

I claim:

1. An air blasting device comprising an elongate container adapted to receive gas under pressure and having vents therein, a vent plugging means in said container adapted to yield to uncover said vents, and a tube for introducing compressed gas into said container, said tube extending longitudinally and into one end of said container and having the end thereof in the container open, said tube having a length in the container equal to at least two-thirds of the length of the container and at least four orifice means in the Wall of said tube communicating the interior of the tube with the container, said orifice means being along substantially the entire length of said tube for introducing into said container along the length thereof masses of compressed gas which are substantially equal to each other, whereby to eflFect equal increase of pressure throughout the length of said container during the filling thereof.

2. An air blasting device comprising an elongate container adapted to receive gas under pressure and having vents therein, a vent plugging means in said container adapted to yield to uncover said vents, and a tube for introducing compressed gas into said container, said tube extending longitudinally and into one end of said container and having the end thereof in the container open, said tube having a length in the container equal to at least four-fifths of the length of the container and having at least seven orifices in the Wall of said tube communicating the interior of said tube with the container, said orifices each being of a diameter equal to one-third of the internaldiameter of said tube, each orifice being further from the adjacent orifice closer the said one end of the container than from the adjacent orifice closer the free end of the tube, the ratios of the spacings between said orifices being 15:10:7:5:3:2.

References Cited by the Examiner UNITED STATES PATENTS SAMUEL FEINBERG, Primary Examiner.

ARTHUR M. HORTON, Examiner. 

1. AN AIR BLASTING DEVICE COMPRISING AN ELONGATE CONTAINER ADAPTED TO RECEIVE GAS UNDER PRESSURE AND HAVING VENTS THEREIN, A VENT PLUGGING MEANS IN SAID CONTAINER ADAPTED TO YIELD TO UNCOVER SAID VENTS, AND A TUBE FOR INTRODUCING COMPRESSED GAS INTO SAID CONTAINER, SAID TUBE EXTENDING LONGITUDINALLY AND INTO ONE END OF SAID CONTAINER AND HAVING THE END THEREOF IN THE CONTAINER OPEN, SAID TUBE HAVING A LENGTH OF THE CONTAINER EQUAL TO AT LEAST TWO-THIRDS OF THE LENGTH OF THE CONTAINER AND AT LEAST FOUR ORIFICE MEANS IN THE WALL OF SAID TUBE COMMUNICATING THE INTERIOR OF THE TUBE WITH THE CONTAINER, SAID ORIFICE MEANS BEING ALONG SUBSTANTIALLY THE ENTIRE LENGTH OF SAID TUBE FOR INTRODUCING INTO SAID CONTAINER ALONG THE LENGTH THEREOF MASSES OF COMPRESSED GAS WHICH ARE SUBSTANTIALLY EQUAL TO EACH OTHER, WHEREBY TO EFFECT EQUAL INCREASE OF PRESSURE THROUGHOUT THE LENGTH OF SAID CONTAINER DURING THE FILLING THEREOF. 